The use and existence of multiple bit tools are well known. Generally and in the case of a screwdriver used manually, the bits are stored in the handle of the screwdriver. To retrieve a bit, the user removes the end-cap of the handle to expose the bits. One difficulty with such tools is that users have difficulty determining the appropriate bit without its removal. Hence, all of the bits are usually emptied from the handle.
Various mechanisms have been devised to select individual bits. In U.S. Pat. No. 4,463,788 to Corona et al, a mechanism includes a rotatable disk at the anterior end of the handle in which a slot acts to guide one bit at a time from the storage chamber, or magazine, into the chuck.
In U.S. Pat. No. 4,572,038 to Graham, a mechanism is described in which the bits are stored in a forward magazine which rotates about a rear retractable driving shaft in order to individually engage the bits stored in the magazine.
In U.S. Pat. No. 3,753,455 to Butler, the bits can be gravity fed from the storage chamber directly into the chuck.